The present invention is related to systems and methods for modifying various non-equidimensional substrates with modifying agents.
Methods have been developed for the coating or modification of various substrates including metals, alloys, organometallics, salts, optical fibers, filaments, cables, glass fibers, graphite fibers, fiberglass, structural polymers, single strand polymers, filamentous polymers, composites, and the like. For example, polystyrene is known to be a good coating for glass optical fibers to increase durability. These coatings, however, are generally applied in a variety of ways with chemical treatment processes. Some of these methods of chemical treatment (for coating, impregnation, surface modification, etc.) include solvent-based systems and melt-based systems. Additionally, with respect to non-equidimensional substrates, thermoplastics and other coatings have been applied by various methods.
Solvent-based chemical treatment systems can include organic or inorganic materials in solutions such as aqueous solutions wherein the organic or inorganic material is dissolved, suspended, or otherwise dispersed in the solution. In the area of coating of glass fibers, U.S. Pat. Nos. 5,055,119, 5,034,276 and 3,473,950 disclose examples of such chemical treatments. Typically, with chemical treatment of some of the prior art, solvents are used to lower the viscosity of the chemical treatment to facilitate wetting of the glass fibers. The solvent is substantially unreactive with the other constituents of the chemical treatment and is driven out of the chemical treatment after the wetting of the glass fibers. In each process for applying solvent-based chemical treatments, an external source such as heat can be used to evaporate or otherwise remove the water or other solvent from the applied chemical treatment, leaving a coating of organic material on the glass fibers. With melt-based chemical treatment systems, thermoplastic-type organic solids can be melted and applied to various fibrous structures. Again, in the area of glass coating, U.S. Pat. Nos. 4,567,102, 4,537,610, 3,783,001 and 3,473,950 disclose examples of such melt-based chemical treatments of glass fibers. These methods and others have been used in the prior art to coat various elongated materials including textile yarns, monofilaments, bundles of monofilaments, and fibrous structures.
Supercritical fluids have been used previously to coat elongated materials such as fibers, metals, and the like. However, when such supercritical fluids have been used, they have typically been applied by one of a few methods. Several of these techniques involve the application of one or more modifying agent by batch soaking in an enclosed chamber. Other methods include processes based upon spraying from a pressurized chamber through a narrow nozzle.
With regard to spray-on deposition, air pressure sprayers have been used to contain supercritical and near-critical fluids (carriers) containing coating material. Upon spraying of the fluid onto the substrate, the supercritical fluid carrying the coating material leaves the high pressure environment and is exposed to a normal atmospheric environment. Thus, the supercritical fluid is exposed to low pressure and evaporates, leaving behind the coating material or modifying agent which modifies the substrate. Examples of typical spray depositions of the prior art include U.S. Pat. Nos. 4,582,731, 4,734,227, 4,734,451, 4,970,093, 5,032,568, 5,213,851, and 5,997,956. Regarding supercritical fluid batch processes, the substrate is typically immersed and then the pressure is dropped, depositing the coating. This is usually followed by a drying stage. In a related embodiment, fluorocarbon polymers can be used to enhance solubility of polar components in supercritical fluid. However, this is still a batch process.
Though the use of liquified gas, supercritical fluids, and near-critical liquids and gases have been used to coat solid or other fibrous substrates in the prior art, none presently known by the applicant appear to provide a system and method for modifying non-equidimensional substrates in a continuous system that does not utilize spray-on or batch coating processes.
The present invention is drawn to a system configured for applying a modifying agent to a non-equidimensional substrate. The system comprises a processing chamber configured for applying a modifying agent to the substrate. A pair of end seals are also disclosed which can be configured for accepting the shape of the non-equidimensional substrate to be coated. For example, if end seals are used and the substrate is flat or sheet-like, then the seals should be large enough and configured appropriately to accept the substrate into the system. Preferably, the seals can be configured to generally match (in a slightly larger manner) the shape of the non-equidimensional substrate such that seal fluids (if used) and process chamber fluids cannot substantially leak into the surrounding atmosphere. A passageway is provided within the device configured for passing the substrate through the first end seal, the processing chamber, and the second end seal in series. Though not required, at least one expansion chamber can be disposed between each of the end seals and the processing chamber.
Additionally, a method of continuously modifying a non-equidimensional substrate with a modifying agent is disclosed. The method of modifying the non-equidimensional substrate comprising the steps of: providing a treatment apparatus chamber having a passageway configured to pass the non-equidimensional substrate entirely therethrough; providing a treatment mixture comprising a modifying composition in a carrier medium, wherein the carrier medium is selected from the group consisting of a supercritical fluid, a near-critical fluid, a superheated fluid, a superheated liquid, and a liquefied gas; passing the non-equidimensional substrate continuously through the passageway; and flowing the treatment mixture into the passageway during movement of the non-equidimensional substrate through the passageway.